The concept that can be used in order to answer this item is that of ratio and proportion. The ratio of the man's height and the length of his shadow should be proportional or equal to the ratio of the tower height and length of its shadow. If we let x be the height of the tower, the equation that would help us solve this item is,
2 / x = 0.5 / 13.5
The value of x is equal to 54. Thus, the tower's height is approximately 54 meters.